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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4.  
  5. typedef struct
  6. {
  7.     float x;
  8.     float y;
  9.     float z;
  10. } vec3;
  11.  
  12. float
  13. dot(vec3 a, vec3 b)
  14. {
  15.     return a.x * b.x + a.y * b.y + a.z * b.z;
  16. }
  17.  
  18. vec3
  19. scale(float s, vec3 a)
  20. {
  21.     vec3 r;
  22.     r.x = s * a.x;
  23.     r.y = s * a.y;
  24.     r.z = s * a.z;
  25.     return r;
  26. }
  27.  
  28. vec3
  29. add(vec3 a, vec3 b)
  30. {
  31.     vec3 r;
  32.     r.x = a.x + b.x;
  33.     r.y = a.y + b.y;
  34.     r.z = a.z + b.z;
  35.     return r;
  36. }
  37.  
  38. int
  39. intersect(vec3 a, vec3 b, vec3 *normals, vec3 *points, int nnormals)
  40. {
  41.     vec3 ab = add(b, scale(-1, a));
  42.     float tfirst = 0;
  43.     float tlast = 1;
  44.     int i;
  45.     for(i = 0; i < nnormals; i++)
  46.     {
  47.         float d = dot(normals[i], points[i]);
  48.         float denom = dot(normals[i], ab);
  49.         float dist = d - dot(normals[i], a);
  50.         float t = dist / denom;
  51.         if(denom > 0 && t > tfirst)
  52.         {
  53.             tfirst = t;
  54.         }
  55.         else if(denom < 0 && t < tlast)
  56.         {
  57.             tlast = t;
  58.         }
  59.     }
  60.     return tfirst < tlast ? 1 : 0;
  61. }
  62.  
  63. const vec3 N = {0,-1,0};
  64. const vec3 S = {0,1,0};
  65. const vec3 W = {-1,0,0};
  66. const vec3 E = {1,0,0};
  67. const vec3 D = {0,0,-1};
  68.  
  69. int
  70. main(void)
  71. {
  72.     vec3 normals[5];
  73.     vec3 player;
  74.     vec3 *targets;
  75.     int i;
  76.     int j;
  77.     vec3 *buildings;
  78.     vec3 *b;
  79.     int nbuildings = 0;
  80.     int n;
  81.     int m;
  82.     char line[300];
  83.     normals[0] = N;
  84.     normals[1] = S;
  85.     normals[2] = W;
  86.     normals[3] = E;
  87.     normals[4] = D;
  88.     fgets(line, 300, stdin);
  89.     n = atoi(line);
  90.     /*5 sides for each building*/
  91.     buildings = calloc(n * 5, sizeof(*buildings));
  92.     b = buildings;
  93.     for(i = 0; i < n; i++)
  94.     {
  95.         char *z;
  96.         fgets(line, 300, stdin);
  97.         for(j = 0; j < n && (z = strtok(j ? NULL : line, " \n")) != NULL; j++)
  98.         {
  99.             vec3 bottom;
  100.             vec3 top;
  101.             if(z[0] == '0') continue;
  102.             nbuildings++;
  103.             bottom.x = j;
  104.             bottom.y = i;
  105.             bottom.z = 0;
  106.             top.x = j + 1;
  107.             top.y = i + 1;
  108.             top.z = atoi(z);
  109.             b[0] = top;
  110.             b[1] = bottom;
  111.             b[2] = top;
  112.             b[3] = bottom;
  113.             b[4] = top;
  114.             b += 5;
  115.         }
  116.     }
  117.     fgets(line, 300, stdin);
  118.     player.x = atof(strtok(line, " "));
  119.     player.y = atof(strtok(NULL, " "));
  120.     player.z = atof(strtok(NULL, " \n"));
  121.     fgets(line, 300, stdin);
  122.     m = atoi(line);
  123.     targets = calloc(m, sizeof(*targets));
  124.     for(i = 0; i < m; i++)
  125.     {
  126.         int hit = 1;
  127.         fgets(line, 300, stdin);
  128.         targets[i].x = atof(strtok(line, " "));
  129.         targets[i].y = atof(strtok(NULL, " "));
  130.         targets[i].z = atof(strtok(NULL, " \n"));
  131.         for(j = 0; j < nbuildings; j++)
  132.         {
  133.             b = &buildings[j * 5];
  134.             if(intersect(player, targets[i], normals, b, 5) == 1)
  135.             {
  136.                 hit = 0;
  137.                 break;
  138.             }
  139.         }
  140.         printf("%d\n", hit ? 1 : -1);
  141.     }
  142.     free(buildings);
  143.     free(targets);
  144.     return 0;
  145. }
Success #stdin #stdout 0s 2428KB
comments (?)
stdin
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5
0 0 0 0 0
0 0 0 0 0
0 0 4 0 0
0 0 0 0 0
0 0 0 0 0
0.5 0.5 0.5
1
4.5 1.5 0.5
stdout
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1
https://ideone.com/MTXpzF
language:
C (gcc 8.3)
created:
9 years ago
visibility:
public

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